Copolycarbonate Compositions with Cyclic and Linear Oligomers and Improved Optical Properties

ABSTRACT

The invention relates to copolycarbonate compositions having cyclic and linear oligomers and improved optical properties, to their use for producing blends and moldings and to moldings obtained therewith.

This invention provides copolycarbonate compositions having cyclic andlinear oligomers, which have improved optical properties, and for theuse thereof for production of blends and moldings and moldingsobtainable therefrom.

Copolycarbonates form part of the group of the technical thermoplastics.They find a variety of uses in the electrical and electronics sector, asa housing material for lights, and in applications where exceptionalthermal and mechanical properties are required, for example hairdryers,applications in the automotive sector, plastic covers, headlamp lensesor light guide elements, and also lamp covers or lamp bezels. Thesecopolycarbonates can be used as a blending partner for furtherthermoplastic polymers.

In the case of these compositions, it is virtually always the case thatgood thermal and mechanical properties such as a high Vicat temperature(heat distortion resistance) and glass transition temperature are anabsolute requirement.

As well as the good thermal and mechanical properties of polycarbonates,high transparency and low intrinsic yellowness (yellowness index, YI)are a further core property of polycarbonates.

These good optical properties have to be maintained even over aprolonged period. This is particularly true of the thermal agingcharacteristics of components. In other words, the long-term performanceunder thermal stress of (co-)polycarbonates is a crucial qualitycriterion of great significance for the use of (co-)polycarbonatecompositions for industrial components. If this criterion is notfulfilled, the (co-)polycarbonate composition and hence the componentare subject to significant thermal yellowing, which is unwanted.

WO 2013/045552 discloses compositions comprising a copolycarbonate basedon bisphenol A and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane(bisphenol TMC).

EP 0 953 605 describes linear polycarbonate compositions having improvedflow characteristics, characterized in that cyclic oligocarbonates areadded in large amounts, for example 0.5% to 4%, and are homogenized bymeans of a twin-screw extruder in the matrix of a linear BPApolycarbonate at 285° C. In this case, flowability increases withincreasing amount of cyclic oligocarbonates. However, this applicationsays nothing about the thermal stability of correspondingpolycarbonates.

EP 2 411 473 describes the use of polyacrylates containing imidestructures for improvement of transmission.

WO 2009/056421 describes the use of polyethers which can likewise bringabout an improvement. However, polyethers have too low an intrinsicthermal stability for use as blend partners in high-temperaturepolycarbonates.

The problem addressed was therefore that of finding compositionscomprising aromatic polycarbonates and having improved opticalproperties, especially low yellowing after heat storage with virtuallythe same heat distortion resistance.

However, the person skilled in the art does not find any pointer in theprior art as to how the optical properties of (co)polycarbonatecompositions or PC blends which are produced in a compounding step canbe improved with a given/defined heat distortion resistance. Moreparticularly, there is no pointer with regard to the influence of theblend component, specifically the influence of specific oligomerstructures present in particular amounts in at least one, on theflowability of the overall mixture.

It has been found that, surprisingly, compositions composed of specific(high-Tg) copolycarbonates (component A; T_(g): glass transitiontemperature) with a further (co)polycarbonate (component B) haveimproved optical properties whenever specific oligomer structures arepresent in component B or in both components.

This is surprisingly true of mixtures in a very large mixing ratio ofthe blend partners.

The novel combinations of properties described are an importantcriterion for the mechanical and thermal performance of theinjection-molded/extruded component. Injection moldings or extrudatesproduced from the copolycarbonate compositions according to theinvention have significantly improved flow properties without anydeterioration in the thermal properties.

Copolycarbonate compositions or blends in the context of thisapplication are understood to mean mixtures of at least onecopolycarbonates and at least one further copolycarbonate orpolycarbonate which may optionally be provided with additives (componentC).

The present invention therefore provides copolycarbonate compositionscomprising, as component

-   A) 5% to 99% by weight of a copolycarbonate containing one or more    monomer units of the formula (1)

-   -   in which        -   R¹ is hydrogen or C₁-C₄-alkyl, preferably hydrogen,        -   R² is C₁-C₄-alkyl, preferably methyl,        -   n is 0, 1, 2 or 3, preferably 3;            as component

-   B) 95% to 1% by weight of a (co)polycarbonate containing one or more    monomer units of the general formula (2):

-   -   in which R³ is H, linear or branched C₁-C₁₀ alkyl, preferably        linear or branched C₁-C₆ alkyl, more preferably linear or        branched C₁-C₄ alkyl, most preferably H or C₁-alkyl (methyl);    -   and    -   in which R⁴ is linear or branched C₁-C₁₀ alkyl, preferably        linear or branched C₁-C₆ alkyl, more preferably linear or        branched C₁-C₄ alkyl, most preferably C₁-alkyl (methyl),        and wherein the (co)polycarbonate of component B) does not have        any monomer units of the formula (1) and the sum total of the        percentages by weight of components A and B in the composition        is 100% by weight;        characterized in that component B contains at least one cyclic        oligomer of the general formula (I) in a total amount of at        least 1.00% by weight, based on the weight of component B

where

-   -   n is an integer from 2 to 6, and    -   Z is a radical of the formula (Ia)

-   -   in which    -   R⁵ and R⁶ are each independently H, C₁-C₈-alkyl, preferably H or        C₁-C₄-alkyl, more preferably hydrogen or methyl, and    -   X is a single bond, C₁- to C₆-alkylene, C₂- to C₅-alkylidene or        C₅- to C₆-cycloalkylidene, which may be substituted by C₁- to        C₆-alkyl, preferably methyl or ethyl, preferably a single bond        or isopropylidene;        and component B contains one or more linear oligomers of the        general formulae (II), (III), (IV), (V) and/or (VI) in a total        amount of 0.50% by weight to 1.40% by weight, based on the        weight of component B,

-   -   where k, l, m, o and p are each independently an integer from 1        to 6 and Z is the radical of formula (Ia) already defined,        wherein the amounts of the structures (I) and (II) to (VI) can        be determined by precipitation and subsequent quantitative HPLC.

Definitions

C₁-C₄-Alkyl in the context of the invention is, for example, methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, C₁-C₆-alkylis additionally, for example, n-pentyl, 1-methylbutyl, 2-methylbutyl,3-methylbutyl, neopentyl, 1-ethylpropyl, cyclohexyl, cyclopentyl,n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1,2-dimethylpropyl,1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl,1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl,2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl,2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl,1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl or1-ethyl-2-methylpropyl, C₁-C₁₀-alkyl is additionally, for example,n-heptyl and n-octyl, pinacyl, adamantyl, the isomeric menthyls,n-nonyl, n-decyl, C₁-C₃₄-alkyl is additionally, for example, n-dodecyl,n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. The same appliesto the corresponding alkyl radical, for example, in aralkyl/alkylaryl,alkylphenyl or alkylcarbonyl radicals. Alkylene radicals in thecorresponding hydroxyalkyl or aralkyl/alkylaryl radicals are, forexample, the alkylene radicals corresponding to the above alkylradicals.

Aryl is a carbocyclic aromatic radical having 6 to 34 skeleton carbonatoms. The same applies to the aromatic moiety of an arylalkyl radical,also called aralkyl radical, and to the aryl constituents of morecomplex groups, for example arylcarbonyl radicals.

Examples of C₆-C₃₄-aryl are phenyl, o-, p-, m-tolyl, naphthyl,phenanthrenyl, anthracenyl or fluorenyl.

Arylalkyl/aralkyl is in each case independently a straight-chain,cyclic, branched or unbranched alkyl radical as defined above, which maybe singly, multiply or polysubstituted by aryl radicals as definedabove.

The above enumerations should be understood by way of example and not asa limitation.

In the context of the present invention, ppb and ppm—unless statedotherwise—are understood to mean parts by weight.

Oligomers

The amounts of the linear oligomers and of the cyclic oligomers can bedetermined as follows: a sample of the polycarbonate composition isdissolved in methylene chloride. By adding acetone, the predominantproportion of the polymer is precipitated. The undissolved fractions arefiltered off; the filtrate is concentrated to dryness. The dry residueis dissolved with THF and the oligomers are determined by HPLC (highpressure liquid chromatography) with UV detection.

The cyclic oligomers of the general formula (I) are present in componentB (based in each case on the total weight of component B and determinedby precipitation and subsequent quantitative HPLC) in a total amount ofat least 1.00% by weight, preferably 1.05% by weight to 1.60% by weight,more preferably 1.10% by weight to 1.50% by weight.

Preferably, the most commonly occurring ring sizes are those with n=3and/or n=4, more preferably n=4.

The total amount of linear oligomers of the general formulae (II),(III), (IV), (V) and (VI) in component B is 0.50% by weight to 1.40% byweight, preferably 0.60% by weight to 1.35% by weight, and morepreferably 0.60% by weight to 1.30% by weight (based in each case on thetotal weight of component B and determined by precipitation andsubsequent quantitative HPLC).

Preferably, the total amount of the cyclic oligomers of the generalformula (I) and the linear oligomers of the general formulae (II),(III), (IV), (V) and (VI) in component B adds up to at least 2.0% byweight, preferably at least 2.2% by weight, and more preferably at least2.4% by weight (based in each case on the total weight of component Band determined by precipitation and subsequent quantitative HPLC).

Component A may likewise include one or more cyclic oligomers of thegeneral formula (I).

Component A may also contain one or more linear oligomers of the generalformulae (II), (III), (IV), (V) and (VI).

Component A

The copolycarbonate composition of the invention contains 5% to 99% byweight, preferably 10% to 95% by weight, and more preferably 15% to 90%by weight (based on the sum total of the parts by weight of components Aand B), of component A.

The monomer unit(s) of the general formula (1) is/are introduced bymeans of one or more corresponding diphenols of the general formula(1a):

in which

-   -   R¹ is hydrogen or C₁-C₄-alkyl, preferably hydrogen,    -   R² is C₁-C₄-alkyl, preferably methyl, and    -   n is 0, 1, 2 or 3, preferably 3.

The diphenols of the formulae (1a) for use in accordance with theinvention and the use thereof in homopolycarbonates are known to somedegree in the literature (DE 3918406).

Particular preference is given to1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC)having the formula (1b):

As well as one or more monomer units of the formulae (1), one or moremonomer unit(s) of the formula (4) may be present in component A:

in which

-   -   R⁷ and R⁸ are each independently H, C₁-C₁₈-alkyl, C₁-C₁₈-alkoxy,        halogen such as Cl or Br or in each case optionally substituted        aryl or aralkyl, preferably H or C₁-C₁₂-alkyl, more preferably H        or C₁-C₈-alkyl and most preferably H or methyl, and    -   Y is a single bond, —SO₂—, —CO—, —O—, —S—, C₁-C₆-alkylene or        C₂-C₅-alkylene, or else C₆-C₁₂-arylene which may optionally be        fused to further aromatic rings containing heteroatoms.

The monomer unit(s) of the general formula (4) is/are introduced via oneor more corresponding diphenols of the general formula (4a):

where R⁷, R⁸ and Y are each as already defined in connection with theformula (4).

Examples of the diphenols of the formula (4a) which can be used inaddition to the diphenols of the formula (1a) include hydroquinone,resorcinol, dihydroxybiphenyls, bis(hydroxyphenyl)alkanes,bis(hydroxyphenyl) sulfides, bis(hydroxyphenyl) ethers,bis(hydroxyphenyl) ketones, bis-(hydroxyphenyl) sulfones,bis(hydroxyphenyl) sulfoxides,α,α′-bis(hydroxyphenyl)-diisopropylbenzenes, and the ring-alkylated andring-halogenated compounds thereof, and alsoα,ω-bis(hydroxyphenyl)polysiloxanes.

Preferred diphenols of the formula (4a) are, for example,4,4′-dihydroxybiphenyl (DOD), 4,4′-dihydroxybiphenyl ether (DOD ether),2,2-bis(4-hydroxyphenyl)propane (bisphenol A),2,4-bis(4-hydroxyphenyl)-2-methylbutane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,1,1-bis[2-(4-hydroxyphenyl)-2-propyl]benzene,1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol M),2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(3-chloro-4-hydroxyphenyl)propane,bis(3,5-dimethyl-4-hydroxyphenyl)methane,2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,bis(3,5-dimethyl-4-hydroxyphenyl) sulfone,2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane,2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane and2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.

Particularly preferred diphenols are, for example,2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4′-dihydroxybiphenyl(DOD), 4,4′-dihydroxybiphenyl ether (DOD ether),1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol M),2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane and2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.

Very particular preference is given to compounds of the general formula(4b)

-   in which R¹¹ is H, linear or branched C₁-C₁₀-alkyl, preferably    linear or branched C₁-C₆-alkyl, more preferably linear or branched    C₁-C₄-alkyl, most preferably H or C₁-alkyl (methyl) and-   in which R¹² is linear or branched C₁-C₁₀-alkyl, preferably linear    or branched C₁-C₆-alkyl, more preferably linear or branched    C₁-C₄-alkyl, most preferably C₁-alkyl (methyl).

Very particular preference is given here to the diphenol (4c).

The diphenols of the general formulae (4a) can be used either alone orin a mixture with one another. The diphenols are known from theliterature or preparable by methods known from the literature (see, forexample, H. J. Buysch et al., Ullmann's Encyclopedia of IndustrialChemistry, VCH, New York 1991, 5th ed., vol. 19, p. 348).

The proportion of the monomer units of the formula (1) in thecopolycarbonate is preferably 0.1-88 mol %, more preferably 1-86 mol %,even more preferably 5-84 mol % and especially 10-82 mol % (based on thesum total of the moles of diphenols used).

The preferred diphenoxide units of the copolycarbonates of component Aderive from monomers having the general structures of theabove-described formulae (1a) and (4a), particular preference beinggiven to the combination of the bisphenols (1b) and (4c).

The copolycarbonate component of the copolycarbonate compositions maytake the form of a block and random copolycarbonate. Particularpreference is given to random copolycarbonates.

The ratio of the frequency of the diphenoxide monomer units in thecopolycarbonate is calculated from the molar ratio of the diphenolsused.

Component B

The copolycarbonate composition of the invention contains 95% to 1% byweight, preferably 90% to 5% by weight, and more preferably 85% to 10%by weight (based on the sum total of the parts by weight of componentsA, B and C), of component B.

Component B is a polycarbonate or a copolycarbonate. (Co)polycarbonatesin the context of the present invention are both homopolycarbonates andcopolycarbonates.

The monomer unit(s) of the general formula (2) are introduced by meansof one or more corresponding diphenols of the general formula (2a):

-   in which R³ is H, linear or branched C₁-C₁₀-alkyl, preferably linear    or branched C₁-C₆-alkyl, more preferably linear or branched    C₁-C₄-alkyl, most preferably H or C₁-alkyl (methyl) and-   in which R⁴ is linear or branched C₁-C₁₀-alkyl, preferably linear or    branched C₁-C₆-alkyl, more preferably linear or branched    C₁-C₄-alkyl, most preferably C₁-alkyl (methyl).

Very particular preference is given here to the diphenol (4c).

As well as one or more monomer units of the general formulae (2), one ormore monomer units of the formula (4) as already described for componentA may be present.

More preferably, component B is based exclusively on the bisphenol (4c).

The copolycarbonate compositions of the invention, given specific ratiosof the components A and B, have improved optical properties (loweryellowing) of the copolycarbonate compositions thus obtained, with ahigh heat distortion resistance in spite of a higher melt viscosity.

This is especially true of compositions in which component B is presentin a concentration of not less than 50% by weight and component Bcontains a chain terminator containing alkyl groups, preferably of theformula (3b).

Preparation Process

Preferred modes of preparation of the (co)polycarbonates which are usedwith preference as component A and B in the composition of theinvention, including the (co)polyestercarbonates, are the interfacialmethod and the melt transesterification method, preference being givento preparing at least one of components A and B by the interfacialmethod.

In a preferred embodiment, at least component A, preferably components Aand B, is/are prepared by the interfacial method.

To obtain (co)polycarbonates of relatively high molecular weight by theinterfacial method, the alkali metal salts of diphenols are reacted withphosgene in a biphasic mixture. The molecular weight can be controlledvia the amount of monophenols, which act as chain terminators, forexample phenol, tert-butylphenol or cumylphenol, more preferably phenol,tert-butylphenol. These reactions give rise to virtually exclusivelylinear polymers. This can be detected by end group analysis. Throughcontrolled use of what are called branching agents, generallypolyhydroxylated compounds, branched polycarbonates are also obtained.

Branching agents used may be small amounts, preferably amounts between0.05 and 5 mol %, more preferably 0.1-3 mol %, most preferably 0.1-2 mol%, based on the moles of diphenols used, of trifunctional compounds, forexample isatin biscresol (IBC) or phloroglucinol,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)hept-2-ene;4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)heptane;1,3,5-tri(4-hydroxyphenyl)benzene; 1,1,1-tri(4-hydroxyphenyl)ethane(THPE); tri(4-hydroxyphenyl)-phenylmethane;2,2-bis[4,4-bis(4-hydroxyphenyl)cyclohexyl]propane;2,4-bis(4-hydroxyphenyl-isopropyl)phenol;2,6-bis(2-hydroxy-5′-methylbenzyl)-4-methylphenol;2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)propane;hexa(4-(4-hydroxyphenylisopropyl)phenyl) orthoterephthalate;tetra(4-hydroxyphenyl)methane;tetra(4-(4-hydroxyphenylisopropyl)phenoxy)methane;α,α′,α′″-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene;2,4-dihydroxybenzoic acid; trimesic acid; cyanuric chloride;3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole;1,4-bis(4′,4″-di-hydroxytriphenyl)methyl)benzene and especially;1,1,1-tri(4-hydroxyphenyl)ethane (THPE) andbis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole. Preference isgiven to using isatin biscresol, and also1,1,1-tri(4-hydroxyphenyl)ethane (THPE) andbis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindol, as branchingagents.

The use of these branching agents gives rise to branched structures. Theresulting long-chain branching usually leads to rheological propertiesof the polycarbonates obtained that are manifested in structuralviscosity compared to linear types.

The amount of chain terminator to be used is preferably 0.5 mol % to 10mol %, more preferably 1 mol % to 8 mol %, especially preferably 2 mol %to 6 mol %, based on moles of diphenols used in each case. The chainterminators can be added before, during or after the phosgenation,preferably as a solution in a solvent mixture of methylene chloride andchlorobenzene (of strength 8%-15% by weight).

To obtain (co)polycarbonates of high molecular weight by the melttransesterification method, diphenols are reacted in the melt withcarbonic diesters, usually diphenyl carbonate, in the presence ofcatalysts, such as alkali metal salts or ammonium or phosphoniumcompounds.

The melt transesterification method is described, for example, in theEncyclopedia of Polymer Science, vol. 10 (1969), Chemistry and Physicsof Polycarbonates, Polymer Reviews, H. Schnell, vol. 9, John Wiley andSons, Inc. (1964), and also DE-C 10 31 512.

In the melt transesterification method, diphenols of the formulae (2a)and optionally (1a) are transesterified with carbonic diesters with theaid of suitable catalysts and optionally further additives in the melt.

Carbonic diesters in the context of the invention are those of theformulae (5) and (6)

where

-   R, R′ and R″ are each independently H, optionally branched    C₁-C₃₄-alkyl/cycloalkyl, C₇-C₃₄-alkaryl or C₆-C₃₄-aryl,    for example    diphenyl carbonate, butylphenyl phenyl carbonate, di(butylphenyl)    carbonate, isobutylphenyl phenyl carbonate, di(isobutylphenyl)    carbonate, tert-butylphenyl phenyl carbonate, di(tert-butylphenyl)    carbonate, n-pentylphenyl phenyl carbonate, di(n-pentylphenyl)    carbonate, n-hexylphenyl phenyl carbonate, di(n-hexylphenyl)    carbonate, cyclohexylphenyl phenyl carbonate, di(cyclohexylphenyl)    carbonate, phenylphenol phenyl carbonate, di(phenylphenol)    carbonate, isooctylphenyl phenyl carbonate, di(isooctylphenyl)    carbonate, n-nonylphenyl phenyl carbonate, di(n-nonylphenyl)    carbonate, cumylphenyl phenyl carbonate, di(cumylphenyl) carbonate,    naphthylphenyl phenyl carbonate, di(naphthylphenyl) carbonate,    di-tert-butylphenyl phenyl carbonate, di(di-tert-butylphenyl)    carbonate, dicumylphenyl phenyl carbonate, di(dicumylphenyl)    carbonate, 4-phenoxyphenyl phenyl carbonate, di(4-phenoxyphenyl)    carbonate, 3-pentadecylphenyl phenyl carbonate,    di-(3-pentadecylphenyl) carbonate, tritylphenyl phenyl carbonate,    di(tritylphenyl) carbonate,    preferably diphenyl carbonate, tert-butylphenyl phenyl carbonate,    di-(tert-butylphenyl) carbonate, phenylphenol phenyl carbonate,    di(phenylphenol) carbonate, cumylphenyl phenyl carbonate,    di(cumylphenyl) carbonate, more preferably diphenyl carbonate.

It is also possible to use mixtures of the carbonic diesters mentioned.

The proportion of carbonic esters is 100 to 130 mol %, preferably 103 to120 mol %, more preferably 103 to 109 mol %, based on the one or morediphenols.

Catalysts used in the melt transesterification method, as described inthe literature cited, are basic catalysts, for example alkali metal andalkaline earth metal hydroxides and oxides, but also ammonium orphosphonium salts, referred to hereinafter as onium salts. Preference isgiven here to using onium salts, more preferably phosphonium salts.Phosphonium salts in the context of the invention are those of thefollowing general formula (7)

where

-   R¹³⁻¹⁶ may be identical or different C₁-C₁₀-alkyls, C₆-C₁₀-aryls,    C₇-C₁₀-aralkyls or C₅-C₆-cycloalkyls, preferably methyl or    C₆-C₁₄-aryls, more preferably methyl or phenyl, and-   X′⁻ may be an anion such as hydroxide, sulfate, hydrogensulfate,    hydrogencarbonate, carbonate, a halide, preferably chloride, or an    alkoxide of the formula OR¹⁷ where R¹⁷ may be C₆-C₁₄-aryl or    C₇-C₁₂-aralkyl, preferably phenyl.

Preferred catalysts are tetraphenylphosphonium chloride,tetraphenylphosphonium hydroxide, tetraphenylphosphonium phenoxide, morepreferably tetraphenylphosphonium phenoxide.

The catalysts are preferably used in amounts of 10⁻⁸ to 10⁻³ mol, basedon one mole of diphenol, more preferably in amounts of 10⁻⁷ to 10⁻⁴ mol.

Further catalysts can be used alone or optionally in addition to theonium salt, in order to increase the rate of polymerization. Theseinclude salts of alkali metals and alkaline earth metals, such ashydroxides, alkoxides and aryloxides of lithium, sodium and potassium,preferably hydroxide, alkoxide or aryloxide salts of sodium. Mostpreferred are sodium hydroxide and sodium phenoxide. The amount of thecocatalyst may be in the range from 1 to 200 ppb, preferably 5 to 150ppb and most preferably 10 to 125 ppb, in each case calculated assodium.

The catalysts are added in solution, in order to avoid excessconcentrations which are harmful in the course of metered addition. Thesolvents are compounds that are inherent to the system and process, forexample diphenol, carbonic diesters or monohydroxyaryl compounds.Particular preference is given to monohydroxyaryl compounds, because itis well known to the person skilled in the art that the diphenols andcarbonic diesters readily undergo change and decomposition at evenslightly elevated temperatures, especially under catalysis. This affectsthe polycarbonate qualities. In the industrially importanttransesterification method for preparation of polycarbonate, thepreferred compound is phenol. Phenol is an obvious option merely becausethe tetraphenylphosphonium phenoxide catalyst used with preference, whenprepared, is isolated as a cocrystal with phenol.

The process for preparing the (co)polycarbonates present in thecomposition of the invention by the transesterification method can beconfigured batchwise or else continuously. After the diphenols of theformulae (2a) and optionally (1a) and carbonic diesters are present inmolten form, optionally with further compounds, the reaction is startedin the presence of the catalyst. The conversion or molecular weight isincreased with rising temperatures and falling pressures in suitableapparatuses and devices by removing the monohydroxyaryl compound whichis eliminated until the desired final state has been obtained. Choice ofthe ratio of diphenol to carbonic diester and of the rate of loss of thecarbonic diester via the vapors and of any added compounds, for exampleof a higher-boiling monohydroxyaryl compound, said rate of loss arisingthrough choice of procedure and the plant for preparation of thepolycarbonate, is what decides the end groups in terms of their natureand concentration.

With regard to the manner in which, the plant in which and the procedureby which the process is executed, there is no limitation or restriction.

Moreover, there is no specific limitation and restriction with regard tothe temperatures, the pressures and catalysts used, in order to conductthe melt transesterification reaction between the diphenol and thecarbonic diester, and also any other reactants added. Any conditions arepossible, provided that the temperatures, pressures and catalysts chosenenable a melt transesterification with correspondingly rapid removal ofthe monohydroxyaryl compound eliminated.

The temperatures over the entire process are generally 180 to 330° C. atpressures of 15 bar, absolute, to 0.01 mbar, absolute.

It is usually a continuous procedure that is chosen, because this isadvantageous for the product quality.

Preferably, the continuous process for preparing polycarbonates ischaracterized in that one or more diphenols with the carbonic diester,and also any other reactants added, using the catalysts, afterpre-condensation, without removing the monohydroxyaryl compound formed,in several reaction evaporator stages which then follow at temperaturesrising stepwise and pressures falling stepwise, the molecular weight isbuilt up to the desired level.

The devices, apparatuses and reactors that are suitable for theindividual reaction evaporator stages are, in accordance with theprocess sequence, heat exchangers, flash apparatuses, separators,columns, evaporators, stirred vessels and reactors or other purchasableapparatuses which provide the necessary residence time at selectedtemperatures and pressures. The devices chosen must enable the necessaryinput of heat and be constructed such that they are able to cope withthe constantly increasing melt viscosities.

All devices are connected to one another by pumps, pipelines and valves.The pipelines between all the devices should of course be as short aspossible and the curvature of the conduits should be kept as low aspossible, in order to avoid unnecessarily prolonged residence times. Atthe same time, the external, i.e. technical, boundary conditions andrequirements for assemblies of chemical plants should be observed.

For performance of the process by a preferred continuous procedure, thecoreactants can either be melted together or else the solid diphenol canbe dissolved in the carbonic diester melt or the solid carbonic diestercan be dissolved in the melt of the diphenol, or the two materials arecombined in molten form, preferably directly from their preparation. Theresidence times of the separate melts of the raw materials, especiallythe residence time of the melt of the diphenol, are adjusted so as to beas short as possible. The melt mixture, by contrast, because of thedepressed melting point of the raw material mixture compared to theindividual raw materials, can reside for longer periods atcorrespondingly lower temperatures without loss of quality.

Thereafter, the catalyst, preferably dissolved in phenol, is mixed inand the melt is heated to the reaction temperature. At the start of theindustrially important process for preparing polycarbonate from2,2-bis(4-hydroxyphenyl)propane and diphenyl carbonate, this temperatureis 180 to 220° C., preferably 190 to 210° C., most preferably 190° C.Over the course of residence times of 15 to 90 min, preferably 30 to 60min, the reaction equilibrium is established without withdrawing thehydroxyaryl compound formed. The reaction can be run at atmosphericpressure, but for technical reasons also at elevated pressure. Thepreferred pressure in industrial plants is 2 to 15 bar absolute.

The melt mixture is expanded into a first vacuum chamber, the pressureof which is set to 100 to 400 mbar, preferably to 150 to 300 mbar, andthen heated directly back to the inlet temperature at the same pressurein a suitable device. In the expansion operation, the hydroxyarylcompound formed is evaporated together with monomers still present.After a residence time of 5 to 30 min in a bottoms reservoir, optionallywith pumped circulation, at the same pressure and the same temperature,the reaction mixture is expanded into a second vacuum chamber, thepressure of which is 50 to 200 mbar, preferably 80 to 150 mbar, and thenheated directly in a suitable apparatus at the same pressure to atemperature of 190 to 250° C., preferably 210 to 240° C., morepreferably 210 to 230° C. Here too, the hydroxyaryl compound formedevaporates together with monomers still present. After a residence timeof 5 to 30 min in a bottoms reservoir, optionally with pumpedcirculation, at the same pressure and the same temperature, the reactionmixture is expanded into a third vacuum chamber, the pressure of whichis 30 to 150 mbar, preferably 50 to 120 mbar, and then heated directlyin a suitable apparatus at the same pressure to a temperature of 220 to280° C., preferably 240 to 270° C., more preferably 240 to 260° C. Heretoo, the hydroxyaryl compound is evaporated together with monomers stillpresent. After a residence time of 5 to 20 min in a bottoms reservoir,optionally with pumped circulation, at the same pressure and the sametemperature, the reaction mixture is expanded into a further vacuumchamber, the pressure of which is 5 to 100 mbar, preferably 15 to 100mbar, more preferably 20 to 80 mbar and then heated directly in asuitable apparatus at the same pressure to a temperature of 250 to 300°C., preferably 260 to 290° C., more preferably 260 to 280° C. Here too,the hydroxyaryl compound formed evaporates together with monomers stillpresent.

The number of these stages, 4 here by way of example, may vary between 2and 6. The temperatures and pressures should be adjusted appropriatelywhen the number of stages is altered, in order to obtain comparableresults. The relative viscosity of the oligomeric carbonate attained inthese stages is between 1.04 and 1.20, preferably between 1.05 and 1.15,more preferably between 1.06 to 1.10.

The oligocarbonate thus obtained, after a residence time of 5 to 20 minin a bottoms reservoir, optionally with pumped circulation, at the samepressure and the same temperature as in the last flash/evaporator stage,is conveyed into a disk or cage reactor and subjected to furthercondensation at 250 to 310° C., preferably 250 to 290° C., morepreferably 250 to 280° C., at pressures of 1 to 15 mbar, preferably 2 to10 mbar, with residence times of 30 to 90 min, preferably 30 to 60 min.The product attains a relative viscosity of 1.12 to 1.28, preferably1.13 to 1.26, more preferably 1.13 to 1.24.

The melt leaving this reactor is brought to the desired final viscosityor final molecular weight in a further disk or cage reactor. Thetemperatures are 270 to 330° C., preferably 280 to 320° C., morepreferably 280 to 310° C., and the pressure is 0.01 to 3 mbar,preferably 0.2 to 2 mbar, with residence times of 60 to 180 min,preferably 75 to 150 min. The relative viscosities are set to the levelnecessary for the application envisaged and are 1.18 to 1.40, preferably1.18 to 1.36, more preferably 1.18 to 1.34.

The function of the two cage reactors or disk reactors can also becombined in one cage reactor or disk reactor.

The vapors from all the process stages are directly led off, collectedand processed. This processing is generally effected by distillation, inorder to achieve high purities of the substances recovered.

This can be effected, for example, according to German patentapplication no. 10 100 404. Recovery and isolation of themonohydroxyaryl compound eliminated in ultrapure form is an obvious aimfrom an economic and environmental point of view. The monohydroxyarylcompound can be used directly for preparation of a diphenol or acarbonic diester.

It is a feature of the disk or cage reactors that they provide a verylarge, constantly renewing surface under reduced pressure with highresidence times. The disk or cage reactors have a geometric shape inaccordance with the melt viscosities of the products. Suitable examplesare reactors as described in DE 44 47 422 C2 and EP A 1 253 163, or twinshaft reactors as described in WO A 99/28 370.

The oligocarbonates, including those of very low molecular weight, andthe finished polycarbonates are generally conveyed by means of gearpumps, screws of a wide variety of designs or positive displacementpumps of a specific design.

Analogously to the interfacial method, it is possible to usepolyfunctional compounds as branching agents.

The relative solution viscosity of the poly- or copolycarbonates presentin the composition of the invention, determined according to DIN 51562,is preferably in the range of 1.15-1.35.

The weight-average molecular weights of poly- or copolycarbonatespresent in the composition of the invention are preferably 15 000 to 40000 g/mol, more preferably 17 000 to 36 000 g/mol, and most preferably17 000 to 34 000 g/mol, and are determined by GPC against apolycarbonate calibration.

Particular preference is given to copolycarbonate compositions in whichcomponent A and/or component B contain, at least in part, as end group,a structural unit of the formula (3a) and/or a structural unit of theformula (3b).

Component C

The present invention further provides compositions comprisingcomponents A and B and optionally, as component C, at least oneadditive, preferably selected from the group of the additives customaryfor these thermoplastics, such as fillers, carbon black, UV stabilizers,IR stabilizers, thermal stabilizers, antistats and pigments, colorantsin the customary amounts; it is optionally possible to improve thedemolding characteristics, flow characteristics and/or flame retardancyby adding external demolding agents, flow agents and/or flameretardants, such as sulfonic salts, PTFE polymers or PTFE copolymers,brominated oligocarbonates, or oligophosphates and phosphazenes (e.g.alkyl and aryl phosphites, alkyl and aryl phosphates, alkyl- andarylphosphines, low molecular weight carboxylic esters, halogencompounds, salts, chalk, talc, silicates, boron nitride, thermally orelectrically conductive carbon blacks or graphites, quartz/quartzflours, glass fibers and carbon fibers, pigments or else additives forreduction of the coefficient of linear thermal expansion (CLTE) andcombination thereof. Compounds of this kind are described, for example,in WO 99/55772, p. 15-25, and in “Plastics Additives”, R. Gächter and H.Müller, Hanser Publishers 1983.

The composition contains generally of organic additives 0% to 5.0% byweight, preferably 0.005% to 2.50% by weight, more preferably 0.005% to1.60% by weight, even more preferably 0.005% to 1.50% by weight, veryespecially preferably 0.005% to 1.0% by weight (based on the overallcomposition), of additives.

If inorganic additives are present in the composition, the total amountof organic and inorganic additives may be up to 30% by weight (based onthe overall composition).

Any demolding agents added to the compositions according to theinvention are preferably selected from the group consisting ofpentaerythritol tetrastearate, glycerol monostearate and long-chainfatty acids, for example stearyl stearate and propanediol stearate, andmixtures thereof. The demolding agents are preferably used in amounts of0.05% by weight to 2.00% by weight, preferably in amounts of 0.1% byweight to 1.0% by weight, more preferably in amounts of 0.15% by weightto 0.60% by weight and most preferably in amounts of 0.20% by weight to0.50% by weight, based on the total weight of components A, B and C.

Suitable additives are described, for example, in “Additives forPlastics Handbook, John Murphy, Elsevier, Oxford 1999”, in “PlasticsAdditives Handbook, Hans Zweifel, Hanser, Munich 2001”.

Suitable antioxidants/thermal stabilizers are, for example:

alkylated monophenols, alkylthiomethylphenols, hydroquinones andalkylated hydroquinones, tocopherols, hydroxylated thiodiphenyl ethers,alkylidenebisphenols, O-, N- and S-benzyl compounds, hydroxybenzylatedmalonates, aromatic hydroxybenzyl compounds, triazine compounds,acylaminophenols, esters ofβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, esters ofβ-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acid, esters ofβ-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid, esters of3,5-di-tert-butyl-4-hydroxyphenylacetic acid, amides ofβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, suitable thiosynergists, secondary antioxidants, phosphites and phosphonites,benzofuranones and indolinones.

Suitable thermal stabilizers are preferablytris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168),tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4′-diylbisphosphonite, triisoctyl phosphate (TOF), octadecyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076),bis(2,4-dicumylphenyl)pentaerythritol diphosphite (Doverphos S-9228),bis(2,6-di-tert-butyl-4-methyl-phenyl)pentaerythritol diphosphite (ADKSTAB PEP-36) and triphenylphosphine (TPP). They are used alone or in amixture (e.g. Irganox B900 or Doverphos S-9228 with Irganox B900 orIrganox 1076 or triphenylphosphine (TPP) with triisoctyl phosphate(TOF)). Thermal stabilizers are preferably used in amounts of 0.005% byweight to 2.00% by weight, preferably in amounts of 0.01% by weight to1.0% by weight, more preferably in amounts of 0.015% by weight to 0.60%by weight and most preferably in amounts of 0.02% by weight to 0.50% byweight, based on the total weight of components A, B and C.

Suitable complexing agents for heavy metals and neutralization of tracesof alkalis are o/m-phosphoric acids, fully or partly esterifiedphosphates or phosphites.

Suitable light stabilizers (UV absorbers) are2-(2′-hydroxyphenyl)benzotriazoles, 2-hydroxy-benzophenones, esters ofsubstituted and unsubstituted benzoic acids, acrylates, stericallyhindered amines, oxamides and 2-(hydroxyphenyl)-1,3,5-triazines orsubstituted hydroxyalkoxyphenyl, 1,3,5-triazoles, preference being givento substituted benzotriazoles, for example2-(2′-hydroxy-5′-methyl-phenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole,2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′,5′-tert-butylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-tert-amyl-phenyl)benzotriazole,2-[2′-hydroxy-3′-(3″,4″,5″,6″-tetrahydrophthalimidoethyl)-5′-methylphenyl]-benzotriazoleand2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol].

Further suitable UV stabilizers are selected from the group comprisingbenzotriazoles (e.g. Tinuvins from BASF), triazine Tinuvin 1600 fromBASF), benzophenones (Uvinuls from BASF), cyanoacrylates (Uvinuls fromBASF), cinnamic esters and oxalanilides, and mixtures of these UVstabilizers.

The UV stabilizers are used in amounts of 0.01% by weight to 2.0% byweight based on the molding composition, preferably in amounts of 0.05%by weight to 1.00% by weight, more preferably in amounts of 0.08% byweight to 0.5% by weight and most preferably in amounts of 0.1% byweight to 0.4% by weight based on the overall composition.

Polypropylene glycols, alone or in combination with, for example,sulfones or sulfonamides as stabilizers, can be used to counteractdamage by gamma rays.

These and other stabilizers can be used individually or in combinationand can be added to the polymer in the forms mentioned.

Suitable flame-retardant additives are phosphate esters, i.e. triphenylphosphate, resorcinol diphosphate, brominated compounds, such asbrominated phosphoric esters, brominated oligocarbonates andpolycarbonates, and preferably salts of fluorinated organic sulfonicacids.

Suitable impact modifiers are butadiene rubber with grafted-onstyrene-acrylonitrile or methyl methacrylate, ethylene-propylene rubberswith grafted-on maleic anhydride, ethyl and butyl acrylate rubbers withgrafted-on methyl methacrylate or styrene-acrylonitrile,interpenetrating siloxane and acrylate networks with grafted-on methylmethacrylate or styrene-acrylonitrile.

In addition, it is possible to add colorants such as organic dyes orpigments or inorganic pigments, carbon black, IR absorbers,individually, in a mixture or else in combination with stabilizers,glass fibers, (hollow) glass beads, inorganic fillers, for exampletitanium dioxide or barium sulfate.

In a particularly preferred embodiment, the composition of the inventioncomprises at least one additive selected from the group consisting ofthe thermal stabilizers, the demolding agents and the UV absorbers,preferably in a total amount of 0.2% by weight to 2.0% by weight, basedon the total amount of components A, B and C. Particular preference isgiven to thermal stabilizers.

The copolycarbonate compositions of the invention are produced instandard machines, for example multi-screw extruders, by compounding,optionally with addition of additives and other admixtures, attemperatures between 280° C. and 360° C.

The (co)polycarbonates and copolycarbonate compositions of the inventioncan be processed in a customary manner in standard machines, for examplein extruders or injection molding machines, to give any desired shapedbodies, or moldings to give films or sheets or bottles.

The copolycarbonate compositions of the invention, optionally in a blendwith other thermoplastics and/or customary additives, can be used togive any desired shaped bodies/extrudates, wherever already knownpolycarbonates, polyestercarbonates and polyesters are used:

-   1. Safety glazing which, as is well known, is required in many    regions of buildings, vehicles and aircraft, and as shields of    helmets.-   2. Production of films and film laminates.-   3. Automobile headlamps, bezels, indicators, reflectors.-   4. As translucent plastics having a content of glass fibers for    lighting purposes. As translucent plastics having a content of    barium sulfate, titanium dioxide and/or zirconium oxide or    high-reflectance opaque compositions and components produced    therefrom.-   5. For production of precision injection moldings, for example    lenses, collimators, lens holders, light guide elements and LED    applications.-   6. As electrical insulators for electrical conductors and for plug    housings and plug connectors.-   7. Housings for electrical appliances.-   8. Protective glasses, eyepieces.-   9. For medical applications, medical devices, for example    oxygenators, dialyzers (hollow fiber dialyzers), 3-way taps, hose    connectors, blood filters, injection systems, inhalers, ampoules.-   10. Extruded shaped bodies such as sheets and films.-   11. LED applications (sockets, reflectors, heat sinks).-   12. As a feedstock for compounds or as a blending partner or    component in blend compositions and components produced therefrom.

This application likewise provides the compounds, blends, shaped bodies,extrudates, films and film laminates made from the copolycarbonatecompositions of the invention, and likewise moldings, extrudates andfilms comprising coextrusion layers made from the copolycarbonatecompositions of the invention.

The examples which follow are intended to illustrate the invention, butwithout restricting it.

EXAMPLES Raw Materials Used:

-   PC 1 is a polycarbonate based on bisphenol A, phenol as chain    terminator, with a melt volume flow rate (MVR) of 12.5 cm³/10 min    (300° C./1.2 kg), and a total content of cyclic oligomers of the    formula (I) and linear oligomers of the formulae (II) to (VI) of    2.58% by weight, where the cyclic component is 1.39% by weight; the    proportion therein with ring size n=3 is 0.26% by weight and with    n=4 is 0.40% by weight.-   PC 2 is a polycarbonate based on bisphenol A, phenol as chain    terminator, with an MVR of 12.5 cm³/10 min (300° C./1.2 kg) and a    total content of cyclic oligomers of the formula (I) and linear    oligomers of the formulae (II) to (VI) of 1.94% by weight, where the    cyclic component is 0.67% by weight; the proportion therein with    ring size n=3 is 0.25% by weight and with n=4 is 0.19% by weight.

PC1 is thus the polycarbonate having the higher proportion of cycles andlinear oligomers.

-   CoPC is a commercially available copolycarbonate based on bisphenol    A and bisphenol TMC, phenol as chain terminator, with an MVR of 17    cm³/10 min (330° C./2.16 kg) (Apec 1745 from Bayer MaterialScience    AG).

The polycarbonate PC2 was prepared in a melt process as follows:

From a reservoir, 8600 kg/h of melt mixture consisting of 4425 kg ofdiphenyl carbonate/h (20 658 mol/h) and 4175 kg of bisphenol A/h (18 287mol/h), with addition of 0.52 kg of the phenol adduct oftetraphenylphosphonium phenoxide with 65.5% tetraphenylphosphoniumphenoxide/h (0.786 mol/h; i.e. 0.0043 mol %) dissolved in 4.5 kg ofphenol/h, are pumped through a heat exchanger, heated to 190° C. andconducted through a dwell column at 12 bar and 190° C. The meanresidence time is 50 minutes. The melt is then guided through anexpansion valve into a separator at 200 mbar. The melt flowing downwardis heated back to 190° C. in a falling film evaporator likewise at 200mbar and collected in a receiver. After a residence time of 20 minutes,the melt is pumped into the next three stages of identical construction.The conditions in the 2nd/3rd/4th stage are 100/74/40 mbar;220°/225°/273° C. and 20/10/10 minutes. The oligomer formed has arelative viscosity of 1.08. All vapors are conducted through pressureregulators into a column under reduced pressure and led off ascondensates. Thereafter, the oligomer is condensed in a downstream diskreactor at 280° C. and 3.0 mbar with a residence time of 45 minutes togive a product of higher molecular weight. The relative viscosity is1.195. The vapors are condensed. From the melt stream, which is guidedinto a further cage reactor, by means of a gear pump, a substream of 150kg of melt/h is branched off, admixed with 150 g of a 5% solution of thequencher of the formula 6 in phenol/h, conducted through a static mixerwith a length-to-diameter ratio of 20 and returned to the main meltstream. Directly after the streams merge, the added quencher isdistributed homogeneously within the entire melt stream by means of afurther static mixer. The melt thus treated continues to be subjected tothe process conditions in a further disk reactor at 290° C., 0.7 mbar,with a mean residence time of 120 minutes, discharged and pelletized.The vapors are condensed in the vacuum system and beyond.

The polycarbonate PC1 was prepared in an interfacial process as follows:

In a pumped circulation reactor, upstream of the pump, via a T-piece, 24000 kg/h of an alkaline bisphenol A solution containing 15% by weight ofbisphenol A (BPA) and 2.1 mol of sodium hydroxide solution per mol ofBPA, and also, via a further T-piece, 1848 kg/h of phosgene dissolved in20 400 kg/h of solvent consisting of 50% by weight of methylene chlorideand 50% by weight of monochlorobenzene were metered in. To maintain thealkalinity, 360 kg/h of 32% sodium hydroxide solution were metered inand the reaction mixture was guided back to the pump through a heatexchanger and an unstirred dwell vessel, with metered addition of theabovementioned streams. By means of flow measurement, the amount pumpedin circulation was determined as being 260 m³/h. The temperature was 36°C. A portion of the emulsion which was as large as the incoming rawmaterials, upstream of the metering points for BPA and phosgene, fromthe dwell vessel was fed to a further pump and pumped through a tubularreactor. To this stream were added 1050 kg/h of sodium hydroxidesolution (32% by weight) and 134 kg/h of p-tert-butylphenol, dissolvedin 536 kg of solvent mixture. After a dwell time of 10 min., 18 kg/h ofN-ethylpiperidine in the form of a 4.8% solution in the solvent mixture(50 parts methylene chloride and 50 parts monochlorobenzene) weremetered in and the emulsion was pumped by means of a further pumpthrough a further tubular reactor. After a dwell time of a further 10min., the emulsion was separated in a separating vessel and thepolycarbonate solution was washed to free it of electrolyte by knownmethods, for example by centrifugal technology. The polycarbonatesolution was concentrated in concentration systems and freed of residualsolvent in a vented extruder.

The copolycarbonate CoPC was prepared analogously to PC1 in aninterfacial process. The BP-TMC to BPA ratio is chosen such that a VICATB temperature of 170° C. is attained.

The copolycarbonate compositions of examples 1-6 based on the rawmaterials PC1 and PC2 and CoPC (Apec 1745) are mixed in a twin shaftextruder at 300° C. in the formulations listed in tables 1 and 2. Thepolymer compositions thus obtained by compounding are pelletized and areavailable for physical polymer characterizations.

Determination of the Content of Cyclic and Linear Oligomers

The sample is dissolved with methylene chloride. By adding acetone, thepredominant proportion of the polymer is precipitated. The undissolvedfractions are filtered off; the filtrate is concentrated to dryness. Thedry residue is dissolved with THF and the oligomers are determined byHPLC with UV detection.

Characterization of the Molding Compositions of the Invention (TestMethods):

The melt volume flow rate (MVR) is determined at 300° C. and load 1.2 kgor at 330° C. and load 2.16 kg with a melt index tester according to ISO1133.

The Vicat temperature VST B50 is determined according to ISO 306, methodB at a heat load of 50 K/h.

The yellowness index YI is determined according to DIN 6167. The opticaltransmission is determined according to DIN 5036 and the turbidityaccording to DIN 53490.

TABLE 1 Copolycarbonate compositions Experiment 1 2 3 4 5 6 CoPC % 75 5025 75 50 25 PC 1 % 25 50 75 — — — PC 2 % — — — 25 50 75

Experiments 1-3 are in accordance with the invention and have the higherproportion of cyclic and linear oligomers. Experiments 4-6 arecomparative examples with respect to the inventive examples 1-3.

TABLE 2 Rheological and thermal properties of the copolycarbonatecompositions Experiment 1 2 3 4 5 6 MVR/330° C./2.16 kg/7 min. 20.6 26.234.0 21.2 29.4 41.1 Vicat VSTB120 [° C.] 162.6 157.7 152.6 163.0 157.0151.4 Vicat VSTB50 [° C.] 161.5 156.7 151.5 161.5 155.2 150.0

The values in table 2 show that the good thermal properties (Vicattemperatures) are maintained even though the proportion of cyclic andlinear oligomers is greater.

TABLE 3 Properties after heat storage at 140°C. Heat storage at 140° C.1 2 3 4 5 6 500 h Transmission % 85.73 86.56 87.46 85.58 85.98 85.67Turbidity % 0.5 0.39 0.43 0.4 0.31 0.41 Y.I. 6.1 6.39 6.88 7.18 9.5912.74 1000 h Transmission % 84.56 85.22 85.73 84.11 83.15 80.75Turbidity % 0.54 0.42 0.42 0.34 0.32 0.35 Y.I. 11.96 12.35 14.2 14.2520.72 29.74 1500 h Transmission % 83.25 83.51 83.2 82.29 79.55 76.47Turbidity % 0.7 0.51 0.44 0.43 0.32 0.38 Y.I. 17.8 19.69 22.94 21.8933.81 43.84

The values in table 3 show that the inventive copolycarbonatecompositions 1 to 3, after heat storage at 140° C. (for 500 h, 1000 h or1500 h), show much lower yellowing—represented by the yellowness indicesYI—than comparative examples 4 to 6.

The higher proportion of cycles and linear oligomers thus leads to alower degree of yellowing. This is surprising since, in the injectionmolding process for production of the test specimens, because of thepoorer flowability, higher thermal stress is produced internally, whichshould lead to thermal damage (yellowing) which should be reflected in ahigher yellowness index after heat storage. Moreover, oligomericconstituents have lower thermal stability, which should likewise have anadverse effect on yellowing in the course of heat storage.

1. A copolycarbonate composition comprising: A) 5% to 99% by weight, based on the total weight of the copolycarbonate composition, of a copolycarbonate containing one or more monomer units of the formula (1):

wherein, R¹ is hydrogen or C₁-C₄-alkyl; R² is C₁-C₄-alkyl; and n is 0, 1, 2, or 3; and B) 95% to 1% by weight, based on the total weight of the copolycarbonate composition, of a (co)polycarbonate containing one or more monomer units of the general formula (2):

wherein, R³ is H, linear C₁-C₁₀ alkyl, or branched C₁-C₁₀ alkyl; and R⁴ is linear C₁-C₁₀ alkyl or branched C₁-C₁₀ alkyl; and wherein component B) does not have any monomer units of the formula (1); wherein component B contains at least one cyclic oligomer of the general formula (I) in a total amount of at least 1.00% by weight, based on the weight of component B:

wherein, n is an integer from 2 to 6; and Z is a radical of the formula (Ia):

wherein, R⁵ and R⁶ are each independently H or C₁-C₈-alkyl and X is a single bond, C₁- to C₆-alkylene, C₂- to C₅-alkylidene, or C₅- to C₆-cycloalkylidene, which may be substituted by C₁- to C₆-alkyl; and component B contains one or more linear oligomers of the general formulae (II), (III), (IV), (V) and/or (VI) in a total amount of 0.50% by weight to 1.40% by weight, based on the weight of component B:

wherein k, l, m, o and p are each independently an integer from 1 to 6; and Z is the radical of the formula (Ia); wherein the amounts of the structures (I) and (II) to (VI) are determined by precipitation and subsequent quantitative HPLC.
 2. The copolycarbonate composition as claimed in claim 1, wherein the one or more cyclic oligomers of the general formula (I) in component B are present in a total amount of 1.05% by weight to 1.60% by weight, based on the weight of component B.
 3. The copolycarbonate composition as claimed in claim 1, wherein the one or more linear oligomers of the formulae (II) to (VI) are present in component B in an amount of 0.60% by weight to 1.35% by weight, based on the weight of component B.
 4. The copolycarbonate composition as claimed in claim 1, wherein the total amount of the cyclic oligomers of the general formula (I) and the linear oligomers of the general formulae (II), (III), (IV), (V) and (VI) in component B adds up to at least 2.0% by weight, based on the weight of component B.
 5. The copolycarbonate composition as claimed in claim 1, wherein the cyclic oligomers of the formula (I) with n=4 comprise the largest proportion of the cyclic oligomers of the formula (I), based on the total amount of the cyclic oligomers of the formula (I) in component B.
 6. The copolycarbonate composition as claimed in claim 1, wherein X is a single bond or isopropylidene and R⁵ and R⁶ are each independently H or C₁-C₄-alkyl.
 7. The copolycarbonate composition as claimed in claim 1, wherein the proportion of the monomer units of the formula (1) in the copolycarbonate is 0.1-88 mol % (based on the sum total of the diphenol monomer units present therein).
 8. The copolycarbonate composition as claimed in claim 1, wherein at least one of components A and B additionally contains monomer units of the formula (4):

wherein R⁷ and R⁸ are each independently H, C₁-C₁₈-alkyl, C₁-C₁₈-alkoxy, a halogen, substituted aryl, or aralkyl; and Y is a single bond, —SO₂—, —CO—, —O—, —S—, C₁-C₆-alkylene, C₂-C₅-alkylene, C₆-C₁₂-arylene, or C₆-C₁₂-arylene which is fused to further aromatic rings containing heteroatoms.
 9. The copolycarbonate composition as claimed in claim 1, wherein component A and/or component B contains, as end group, a structural unit of the formula (3a) and/or (3b):


10. The copolycarbonate composition as claimed in claim 1, wherein R¹ is hydrogen and R² is methyl and n is
 3. 11. The copolycarbonate composition as claimed in claim 1, wherein component A contains monomer units derived from compounds of the general formulae (1b) and (4c):

and, in the monomer units of the general formula (2) of component B, R³ is H and R⁴ is linear C₁-C₆ alkyl or branched C₁-C₆ alkyl.
 12. The copolycarbonate composition as claimed in claim 1, wherein 0% to 5% by weight, based on the total weight of the copolycarbonate composition, of organic additives is present in the composition.
 13. The copolycarbonate composition as claimed in claim 1, wherein at least one additive from the group consisting of thermal stabilizers, demolding agents, and UV absorbers is present.
 14. An article comprising a blend, molding, bezel, reflector, indicator, lens, screen/display cover, LED, extrudate, film, film laminate, or coextrusion layer comprising the copolycarbonate composition as claimed in claim
 1. 15. A molding, extrudate, film, or film laminate comprising the copolycarbonate composition as claimed in claim
 1. 16. A molding, extrudate, or film comprising coextrusion layers comprising the copolycarbonate composition as claimed in claim
 1. 